Cast ferrous material of high magnetic permeability



May 20, 1969 Kilo -Lines/ sq. in.

H. B. LAUDENSLAGER, JR., E AL 3,445,299

CAST FERROUS MATERIAL OF HIGH MAGNETIC PERMEABILITY Filed July 22, 1968 Fig.l.

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Sheet drz AMP Turns/ inch lNvEN'roRs Harry B. Luudensluqer,Jr. 8 Everett \MHole y 20, 1969- H. a. LAUDENSLAGER, JR., ET AL 3,445,299

CAST FERROUS MATERIAL OF HIGH MAGNETIC PERMEABILITY Filed July 22, 1968 Sheet 2 of 2 Fig.2.

INVE NTORS Harry B. Loudensloger,Jr. 8:

Everett W. Hole g W United States Patent 3,445,299 CAST FERROUS MATERIAL OF HIGH MAGNETIC PERMEABILITY Harry B. Laudenslager, Jr., Jamestown, and Everett W.

Hale, Falconer, N.Y., assignors to Blackstone Corporation, a corporation of New York Continuation-impart of application Ser. No. 402,570, Oct. 8, 1964. This application July 22, 1968, Ser. No. 756,699

Int. Cl. C22c 39/24 US. Cl. 148-3155 4 Claims ABSTRACT OF THE DISCLOSURE A cast ferrous material of high magnetic permeability comprising about 0.5% to 0.95% carbon, about 2.5% to 4.5% silicon, up to about 0.05% chromium, up to about 0.03% sulfur, up to about 0.05% phosphorus, up to about 0.6% manganese, up to about 0.05% magnesium and the balance iron with usual impurities in ordinary amounts, said carbon being in the form of temper carbon and ferrite substantially free of pearlite and the material being characterized by a permeability of at least 100 kilo lines/in. at 200 ampere turns per inch.

This application is a continuation-in-part of our copending application Ser. No. 402,570, filed Oct. 8, i964 and now abandoned.

This invention relates to a cast ferrous material of high magnetic permeability and particularly to a composition.

of iron and a method of making such iron.

We have discovered a composition and a method of making a workable cast ferrous material which has improved magnetic permeability properties approaching, if not equaling, those of worked silicon steel. We have discovered that a cast ferrous material falling within the following composition limits and treated as hereafter described will have high magnetic permeability. The composition of such a ferrous material should fall within the following broad limits:

Percent Carbon 0.50.95 Silicon 2.54.5 Chromium (max.) Up to 0.05 Sulfur (max.) Up to 0.03 Phosphorus (max.) Up to 0.05 Manganese (max.) Up to 0.6 Magnesium Up to 0.05

The balance iron with usual impurities in ordinary amounts.

A preferred narrower range of composition is:

Percent Carbon 0.65-0.85 Silicon 2.5-3.5 Chromium (max.) Up to about 0.05 Sulfur Up to 0.008 Phosphorus Up to 0.05 Manganese Up to 0.3 Magnesium 0.0200.05

The balance iron with usual impurities in ordinary amounts.

The iron must be annealed as in a malleable iron annealing cycle or treated in some modified heat treatment that will accomplish an anneal or its equivalent so that the carbon is tempered and substantially completely free of combined carbon and flaked graphite after annealing. The melt is preferably agitated so as to react any oxygen in the system with silicon and/or magnesium and separate it as a part of the slag prior to casting. It is important that the iron be substantially free from oxygen and oxides and that the sulfur and phosphorus be reduced to within the ranges above stated. The desired purging action may be accomplished by adding the deoxidizer (silicon or magnesium) into the molten metal with nitrogen or suitable inert gas so that the gas agitates the bath as the deoxidizer enters it and promotes reaction with the oxygen of the bath. As this practice is carried out, it is important that where magnesium is used there be added a sufficient amount of magnesium to provide not more than the residual magnesium set out in the foregoing compositions. We have found that magnesium is desirable, but not always required, as a stabilizer of carbon within the range here set out.

The ordinary impurities referred to in the composition are those which normally appear in the foundry as a result of the addition of remelt scrap. They may include small amounts of nickel, chromium, copper, tin, aluminum, boron, calcium and the like in the small amounts generally recognized as acceptable in malleable practice. In no case, however, can the chromium exceed 0.05% and the nickel or copper exceed 0.5 if maximum performance is desired.

This invention may perhaps best be understood by reference to the following examples. In each case a white cast iron composition was prepared with an appropriate base chemistry. This metal was tapped from the furnace at a temperature between 2880 F. and 2890" F. into a thousand pound ladle. An amount of calcium hearing ferrosilicon x 12 mesh was added to the metal in the ladle suflicient to provide the desired silicon level. Nitrogen or a suitable inert gas was then injected into the ladle through a carbon tube (any other refractory tube such as ceramic might be substituted for the carbon tube) to agitate the metal and pure magnesium spheres were added to the nitrogen or inert gas in the total amount sufficient to achieve the desired magnesium level through the injection tube. The metal was then poured into castings without further treatment. The castings were annealed by a normal annealing cycle for malleable iron. The first stage graphitization was accomplished in about 3 hours at a temperature of 1600 F. The castings were then air quenched to 1300 F. and held for 5 hours and then air cooled to room temperature. As soon as the castings were cool enough to be handled, a ring was machined from the casting, wound and tested on a flux meter according to ASTM specification #341-49-4B for flux testing of ferrous metal. Tests on these castings were compared with like tests on Grade A malleable made to ASTM 35018 specifications and with SAE 1006 steel.

Castings made from metal within the composition range here disclosed and annealed by any good first-class heat treatment for malleable iron, or by a short cycle malleabilization treatment such as that disclosed in the example, will produce high permeability equal or superior to that for SAE 1006 steel. The test data comparing conventional Grade A malleable, SAE 1006 steel and the irons made according to this invention is plotted in FIG- URE 1 which accompanies this application. It will be seen from a comparison of this test data that the iron of this invention has permeability properties far superior to that of ordinary malleable irons and comparable or superior to magnetic types of worked silicon steel.

In FIGURE 1, the several materials represented have the following compositions:

ferrd practices and embodiments in the foregoing specification, it will be understood that this invention can be otherwise practiced within the scope of the following claims.

We claim:

1. A cast ferrous material of high magnetic permeability consisting essentially of about 0.5% to 0.95 carbon, about 2.5% to 4.5% silicon, up to about 0.05% chromium, up to about 0.03% sulfur, up to about 0.05% phosphorus, up to about 0.6% manganese, up to about 0.05% magnesium and the balance iron with usual impurities in ordinary amounts, said carbon being in the form of temper carbon and ferrite substantially free of pearlite and the material being characterized by a permeability of at least 100 kilo lines/in. at 200 ampere turns per inch.

2. A cast ferrous material of high magnetic permeability consisting essentially of about 0.65% to 0.85% carbon, about 2.5% to 3.5% silicon, up to about 0.05% chromium, up to about 0.008% sulfur, up to about 0.05

phosphorus, up to about 0.3% manganese, up to about TABLE I Kilo lines/in.

At 40 At 200 Curve Material 0 Si Mn S Mg Cr amp turns amp turns A Alloy of invention 0. 78 3. 92 0. 45 0.026 0. 040 0. 027 92. 8 108. 2 B do 0. 66 3. 27 0. 50 0. 026 0. 021 0.035 95. 0 113. 8 C do. 0. 68 3. 26 0. 46 0. 024 0. 040 0. 042 93. 0 113. 5 D -do 0. 50 3. 06 0. 50 0. 024 0. 021 0. 041 94. 0 111. 5 F SAE 1006 steel 0. 08 0. 0. 04 86. 5 106. 0 G Conventional grade A malleab 2.18 1. 52 0. 30 0. 063 No 0. 03 80. 5 99. 5 H Conventional grade B malleable" 2. 60 1. 72 0. 28 0. 048 No 0. 03 72. 5 91. 5

While we normally prefer to add magnesium as described above, it is not necessary to the full utilization of our invention when the carbon equivalent is below 2.25 (carbon equivalent=carbon+ x [silicon+phosphorus]) as the following examples will show.

A white iron composition was prepared with an appropriate base chemistry. The metal was tapped from the furnace at a temperature between 2880 F. and 2890 F. into a thousand pound ladle. An amount of 85% calcium bearing ferrosilicon x 12 mesh was added to the metal in the ladle to provide the desired silicon level. The metal was poured into castings without further treatment. The castings were annealed as in the case of the preceding examples.

The permeability was determined as in the case of the alloys shown in Table I and are as follows:

The material of this invention has proved satisfactory for use as a substitute for worked silicon steel in the formation of alternators for passenger cars, trucks and the like, a service for which no cast iron was acceptable prior to the present invention.

It is important that there be no cold working of the cast material after the annealing cycle. If there is any cold working of the casting, it must be re-annealed so that all of the grain structure which has been altered by working is restored.

In FIGURE 2 we show a photomicrograph at 100x of the alloy identified as C hereinabove after the malleable heat treatment. It will be noted that the carbon appears in the temper of blackheart form typical of a malleable lIOI'l.

While we have illustrated and described certain preability of at least 100 kilo lines/in. at 200 ampere turns per inch.

3. A cast ferrous material of high magnetic permeability consisting essentially of about 0.5% to 0.95% carbon, about 2.5% to 4.5% silicon, up to about 0.05% chromium, up to about 0.03% sulfur, up to about 0.05% phoshorus, up to about 0.6% manganese, about 0.02% to about 0.05% magnesium when the carbon equivalent exceeds 2.25, and the balance iron with usual impurities in ordinary amounts, said carbon being in the form of temper carbon and ferrite substantially free of pearlite and the material being characterized by a permeability of at least 100 kilo lines/in. at 200 ampere turns per inch.

4. A cast ferrous material of high magnetic permeability consisting of about 0.65 to 0.85% carbon, about 2.5 to 3.5% siilcon, up to about 0.05% chromium, up to about 0.008% sulfur, up to about 0.05% Phosphorus, up to about 0.3% manganese, about 0.02% to about 0.05% magnesium when the carbon equivalent exceeds 2.25, and the balance iron with usual impurities in ordinary amounts, said'carbon being in the form of temper carbon and ferrite substantially free of pearlite and the material being characterized by a permeability of at least 100 kilo lines/in. at 200 ampere turns per inch.

References Cited UNITED STATES PATENTS 2,069,423 2/ 1937 Schwartz l23 2,578,794 12/1951 Gagnebin et al. 75l23 2,610,912 9/1962 Millis et a1. 75l23 2,873,188 2/1959 Bieniosek 75130 3,080,228 3/1963 Hale et a1. 75130 3,189,492 6/1965 Laudenslager et a1. 148138 3,189,443 6/1965 Laudenslager et al. l48l39 L. DEWAYNE RUTLEDGE, Primary Examiner.

P. WEIN STEIN, Assistant Examiner.

US. Cl. X.R. 

